Chitin is the second most abundant natural biopolymer in the world, next only to cellulose, and the most abundant naturally occurring polysaccharide that contains amino sugars. Chitin is found as a component of crustacean shells, insect exoskeletons, fungal cell walls, microfauna, and plankton. The various sources of chitin differ somewhat in their structure and percent chitin content. Chitin naturally occurs in association with proteins and minerals such as calcium carbonate.
Chitin is a polymer formed primarily of repeating units of beta(1-4) 2-acetamido-2-deoxy-D-glucose (or N-acetylglucosamine or GlcNAc). Approximately 16% of the naturally occurring chitin polysaccharide units are deacetylated.
Most commercial applications involving chitin make use of its deacetylated derivative, called chitosan. Chitosan is a polysaccharide formed primarily of repeating units of beta(1-4) 2-amino-2-deoxy-D-glucose (or D-glucosamine). Unlike most polysaccharides, chitosan has a positive charge. This charge is the result of the amino groups contained in chitosan taking on hydrogen ions at low pH. Generally, about 80% of the chitosan polysaccharide units are deacetylated and 20% remain acetylated. These values vary according to the chitin sources and methods by which the polysaccharide is processed. Chitosan is produced by hydrolyzing the N-acetyl linkage in chitin with concentrated alkali and then rinsing away the alkali by slurrying the material with water.
The vast commercial potential for applications using chitin and chitosan biopolymers has only recently been realized. Commercial uses for chitin and chitosan include pharmaceuticals and other aspects of health care such as wound care products, and medical implants, as well as applications in agriculture, cosmetics, food additives and separations, textiles, and water and waste water treatment.
Applications which take advantage of the biocompatibility and bioactivity of chitin and chitosan exemplify the numerous useful applications of these biopolymers. For example, by inhibiting the formation of fibrin strands in wounds, chitosan inhibits the formation of scar tissue. Because of this property, chitosan, along with chitin, can be used to form sutures, dressings, and other healing agents with properties not found in competing products. Additionally, since lysozyme present in wounds breaks down chitin, sutures and wound dressing can be made that will break down instead of needing to be removed. The bioactivity properties of chitin and chitosan is also important in nonmedical applications. For example, chitin stimulates soil microorganisms to produce enzymes that break down chitin. These enzymes attack pesticidal organisms such as soil nematodes that contain chitin as part of their structure. Additionally, chitin has been found to stimulate the growth of bacteria in the gut, a property that could have application for food, feed and cell culture.
Chitin also has potential applications in the textile industry. Recently, a novel chitin fabric called "Biochitin" has been developed. Biochitin, is a highly breathable fabric consisting of chemically treated chitin applied to a porous polyurethane resin coated on a nylon sheet. The chitin layer serves to absorb perspiration, and has over twice the water-absorbing capacity of conventional materials.
The current commercial source of chitin and chitosan is shellfish waste. Fungi also provide a potential major source of chitin which can be derived from fermentation wastes or grown specifically for chitin/chitosan manufacture. Methods have been developed for extracting chitin from fungus, although this process has not been implemented on a commercial scale.
Extraction of chitin from fungi provides a more controllable route to get a purer and more consistent chitin than obtained from shellfish waste. Furthermore, chitin extracted from fungi is less likely to include allergenic contaminants than seafood derived chitin and is therefore more suitable for use in textile, food and pharmaceutical applications. There is therefore a great need for identifying fungal sources which produce quantities of chitin sufficient to justify commercial scale up, and to harvest the chitin produced by these fungal sources.
There are presently twenty-two described genera in the Mucoraceae family. Members of this family are characterized as follows;
reproduction asexually by aplanospores (nonmotile sporangiospores), asexual spores are not conidia; saprobic, not mycorrhiza, many spored sporangia present, sporangial wall not splitting into 2 halves, sporangia globose, sporangia wall thin, sporangia with a distinct columella, without sporangiola (Ainsworth, G. C., F. K. Spparow, A. S. Sussman, 1973, "The Fungi, An Advanced Treatise. Volume 4B, A Taxonomic Review with Keys: Basidiomycetes and Lower Fungi", Academic Press, Inc. London).